There is well known prior art in all the fields cited above, including ferry boats having multiple decks with a plurality of lanes on each deck.
The patents listed below are a sampling of the prior art:
U.S. Pat. Nos. 1,799,456 2,672,840 3,742,888 4,008,675 4,227,475 4,196,686 4,422,517 4,766,829 5,146,863 5,415,120 PA1 Japan 60-163788 PA1 Soviet Union SU-532-548 PA1 British 895-341
U.S. Pat. No. 3,590,762 issued to Yuan discloses a land and water based vehicle equipped with hydro/air foils generally oval in shape with slotted trailing edges for jet flow therefrom and for circulation control of the flow around the foil to impart high lift to the foil for controlling the vehicle without the necessity for changing the angle of attack of the foil.
U.S. Pat. No. 3,742,888 issued to Crowley discloses a soft riding-stable multiple-chamber air cushioned boat hull having a plurality of high pressure air chambers around the periphery automatically providing heave stability as well as roll and pitch stability. The hull may further include a vent slot proving a means for exhausting the spill out of the continuously charged high pressure chambers and further makes a sharp reduction in the bow wave pressure. In addition to providing stability the high pressure chambers lift the boat providing a low friction, soft riding air cushioned support.
U.S. Pat. No. 3,968,762 issued to Meyer, Jr. teaches a water craft combining the physical and hydrodynamic features of a catamaran, hydrofoil and rigid sidewall air cushioned vehicle. The water craft is intended to operate as a multi-modal vehicle in the approximate speed range of 0-100 knots. The vehicle from at rest to operational speed, obtains its lift at first from 100% buoyancy of catamaran hulls, then from dynamic lift of hydrofoils, and finally from powered aerostatic lift from a captured air cushion. A combination of two or all lift modes may be used through speed changes and at intermediate speeds.
U.S. Pat. No. 4,008,675 issued to Johansson discloses a ship comprising a hull in which vehicles can be readily loaded and unloaded from at least two ramps at about the same level, the ramps communicating with a cargo-carrying portion extending through two decks and comprising fully separated cargo volumes, in which straight blind alleys emanating from lobbies within the hull at opposite ends of the hull communicate with mutually inclined decks extending upwardly and downwardly forward-aft and aft-forward, respectively, and in communication with respective opposite lobbies.
U.S. Pat. No. 4,196,686 issued to Moran teaches a sidewall drag reduction system for captured air bubble type surface effect ships having rigid surface-piercing sidewalls. Pressurized air is discharged vertically down into the surface effect ship air cushion chamber from platform ports, and horizontally into the air cushion chamber from nozzles located near the bottom of the internal surface of the sidewalls.
U.S. Pat. No. 4,422,517 issued to Hammerschlag discloses bow and stern seals for sidewall type air cushion vehicles for contacting , together with the sidewalls, the air cushion under the vehicle. They consist of a substantial number of more or less equidistant rods connected by flexible membranes, these rods being designed to hinge around a more or less common axis at substantially the top of the air cushion, the rods extending beyond their hinge points and being positioned by two sets of opposing air bags, one set of air bags acting on the extensions of the rods above the hinge points and the other set on the sections of the rods just below the hinge points. The membranes are attached with a large amount of slack so that the rods can rotate a very substantial amount relative to each other. As the air bags will allow the rods only to rotate a limited amount relative to each other, the membranes will not get tight, and the membranes and rods will not be exposed to the accompanying shock loads leading to membrane tear and rod breakage. The bags react upon the ship structure, which has air chambers connected to the bags with openings that can be closed off partially or completely, to change the response characteristics of the air bags and thereby of the seal.
U.S. Pat. No. 4,227,475 issued to Mattox discloses a waterborne air cushion vehicle having a flat rigid upper rectangular sheet like platform, a plurality of flat rigid longitudinal walls attached substantially at right angles thereto and depending therefrom substantially parallel with the major axis of the platform. The outermost two walls are disposed as sidewalls along respective edges of the platform. The vehicle is provided with flexible trough shaped skirts which are independently movable with respect to the walls. A source of pressurized air forces air into the skirts and also into air cushion chambers located beneath the platform. The flexible skirts provide for less shock and resistance from wave formations due to the compression of the skirts.
U.S. Pat. No. 4,350,107 issued to Mattox teaches a water borne air cushion vehicle having a flat rigid upper rectangular sheet-like platform, and a plurality of flat rigid longitudinal walls attached substantially at right angles thereto and depending therefrom substantially parallel with the major axis of the platform. Two of the walls are disposed as side walls along respective edges of the platform, and a plurality of longitudinally spaced laterally aligned arrays of flexible trough-shaped skirts are looped with a space therein and fastened along the longitudinal edge of the underside of the platform flush with, but movable with respect to adjacent pairs of the walls. The skirts are extendible to a lesser depth than that of the walls, and a source of pressurized air is admitted through apertures of fixed size at a relatively high pressure to the skirts. Also, low pressure air is admitted through variable sized openings remotely controlled and located beneath the platform in communication with at least four square or rectangular open bottom air cushion chambers disposed laterally in pairs. Each of the four square air cushion chambers is bounded by an adjacent pair of skirts and by an adjacent pair of walls, the depth of the walls and of the skirts being so related to the flow rate of the air that the vehicle is buoyant upon water. The walls protrude into the water sufficiently to prevent air spillage when the vehicle is urged longitudinally through the water by a propulsion system. The skirt air inlet openings are adapted to re-admit by reverse flow at least part of the compressed air in any one of the skirts independently in response to fugitive deflection of the skirts. The skirts are bag like structures attached along one side to the underside of the platform via a brace comprising a flexible sheet extending through the width of the skirt.
U.S. Pat. No. 4,766,829 issued to Schlichthorst discloses a catamaran-type cushion craft having two floats arranged space apart parallel to one another which are connected together at the top by a connecting structure which carries built in structures and which is sealed at the bottom by an air tight transverse deck. The connecting structure includes at least two transverse trussed girders arranged spaced apart behind one another, which at least partially contain transverse hollow cavities for passageways and line accommodating hollow cavities, with containers and longitudinal passage and supply elements being mounted at the front and/or rear sides of the double transverse trussed girders.
U.S. Pat. No. 5,146,863 issued to Ford discloses an air cushion displacement hull water vehicle that defrictionizes water flowing under the hull as the vehicle is propelled through the water. The hull includes a forward bow portion, an opposing aft end portion, a pair of sidewalls spaced from each other and extending there between the forward bow portion and the aft end portion, and a bottom wall extending between the forward bow portion and the aft end portion and between the pair of sidewalls. The bottom wall of the hull is recessed to define an air cushion region. An air supply device positioned within the interior of the hull communicates with the hull cushion region and is operable to supply pressurized air to the air cushion region to defrictionize water flow under the air cushion region.
U.S. Pat. No. 5,415,120 issued to Burg teaches a marine surface vehicle that includes pressurized supporting gas cushions in multiple hulls, normally catamaran-like sidehulls, where such pressurized supporting gas cushions support a majority of boat weight in operation. The preferred embodiment of the invention utilizes long fine pointed bow catamaran-like sidehulls that are in mechanical communication with a connecting hull structure. The long fine sidehulls offer performance advantages over a single large supporting gas cushion. Sidehull gas cushion outer sidewalls are preferably wider and deeper than inner sidewalls which insures maximum resistance coupled with maximum transverse stability in roll. Further, sidehull gas cushioned sidewalls optionally have angled to horizontal flatter surfaces forward and then transition to more rounded shapes aft which provides for a good pitch stability and minimum hydrodynamic resistance. The invention may include a hull on centerline that adds to stability in rough seas and gives a racy yacht-like appearance. Recesses in the sidehulls may include, at least in part, fixed and/or movable seals. Fixed seals may include inset vented steps to reduce wetted surface area. The recess gas pressurization system may include a controller to control pressures in individual recesses which allows at least some control of boat motions in rough seas. A further feature is the use of vertically oriented vented steps in the sides of the sidehulls to reduce wetted area drag when operating in rough seas. Another feature is the use of air flow turbulence generators on the underside, or wet deck, of the connecting hull structure to thereby increase static pressure lifting forces acting on the connecting hull structure.
PCT application No. WO 90/05660 filed by Brown discloses a ferry vessel having a main vehicle deck space and twin extended longitudinal casings having at their extremities large longitudinally closing watertight doors to divide the main vehicle space into three watertight compartments thereby limiting possible flooding of the vehicle deck in a side compartment due to damage such as collision, or to the center compartment upon breaching of bow or stern door. In the event of center compartment flooding, the intact outboard compartments provide substantial righting moment against listing. To further reduce the likelihood of flooding arising from side damage, the vehicle deck levels outboard of the casings may be raised to increase the vehicle's freeboard and the hull subdivision transverse bulkheads carried up such that their tops form a stepped V. Still further reduction of floodable areas is achieved by a system of transversely located floodgates.
Japanese patent publication 60-163788 discloses a car ferry with car carrying decks arranged in multilayers in a ship. The car carrying decks are formed into multiple band like partial decks serving as travel paths for car wheels. The band like partial decks are fitted on support cross beams arranged at a distance from each other. Since the car carrying decks are arranged only where car wheels are located, the hull weight can be largely reduced and the production cost of the hull can be decreased.
Russian patent publication No. SU-532-548 teaches a multideck car ferry having loading recesses that are positioned one above another on both sides of the ship. Ramps are mounted in loading recesses for car access to the main deck of the ship.
In metropolitan areas involving islands and related waterways, increasing population generates increasing needs to facilitate traffic flow across the waterways. These needs can be met by building bridges and/or by using and improving ferry systems. Obviously each approach to meeting the increasing needs has its relative advantages and disadvantages.
A need thus exists to improve the ratio of advantages to disadvantages for ferry systems, particularly the vessels used in the system, by improving the ratio of traffic flow rate capability of the vessels relative to their sizes as expressed in terms of their displacements.
A further need exists for a vessel capable of high speed, such as 40 to 50 knots, without creating unacceptable wake and with a low power to weight ratio and good fuel efficiency.
An additional need exists for a maximized ratio of usable to total deck space.
Another need exists for traffic flow onto, through and off the vessel virtually free of impediment caused by lane changing and/or use of ramps and ramp adjustment.
A final need exists for a vessel that is economical to construct and operate, and provides passenger comfort.